Medical implant devices are often made from biodegradable polyesters, such as poly(lactide), poly(glycolide), poly(lactide-co-glycolide), and poly(caprolactone). Such devices can be implanted into a human or other subject to provide a wide variety of therapeutic benefits. The devices can help a bone to heal, deliver a drug, function as a fluid pump, stimulate electrical signals, as well as many other functions. Devices made from biodegradable polyesters provide the added advantage of being non-toxic and readily degradable and secretable from the subject once the lifetime of the device is over, or once the therapeutic effect is achieved. Biodegradable devices can be formulated so as to degrade over a relatively wide range of time periods, such as hours and up to months or even years.
Polyesters of biodegradable implant devices are susceptible to hydrolysis by water. Water can absorb into a device and thereby come in contact with the polyester even after a brief exposure of the device to a normal atmosphere. When water does come into contact with polyesters, hydrolysis is likely to occur. As a result of hydrolysis, polyesters break-down or degrade into smaller subunits of the polymer. Such degradation, induced by hydrolysis, severely affects a number of properties of the device, such as the mechanical strength of the device, cohesiveness of the device, or can even cause the unwanted release of a substance, such as a drug, that is present within the device. Residual moisture resulting from a process for preparing a device or moisture that is later absorbed into the device can thus reduce the shelf-life of the device and adversely affect device performance.